Seal



Oct. 9 E. J. G. BEESON SEAL - Filed Nov. 14, 1939 Fig. 5.

eorge Beeson,

Fig. 2

- a seal comprising my r the like, may be secured,

Patented ct.'29, 1940 UNITED STATES SEAL Eric John George Bceson,Southwell, England, assignor to General Electric Company, a corporationof New York Application November 14, 1939, Serial Nb. 304,352 In GreatBritain October 31, 1938 2 Claims. (01. 176-50) My invention relates tothe sealing conductors into vitreous envelopes. More particularly theinvention relates to seals for envelopes which have to withstand hightemperatures and therefore have to be made of quartz or high meltingpoint glass.

One object of my invention is to provide a preformed seal which can besealed into an envelope when required.

The invention consists in sealing a conductor in a stem of refractoryvitreous material, such as quartz or hard glass, with a lead orconducting member projecting from one end which may form an electrode towhich an electrode, filament or and a connecting lead extending throughthe other end but enclosed in an evacuated chamber formed integral withthe stem which prevents the connecting lead from being damaged oroxidized. The invention further consists in so forming the seal that itcan be fused into an aperture in an envelope without the heat necessaryfor the fusion oxidizing or otherwise damaging the conductors projectingfrom it.

The invention will be better understood by reference to the accompanyingdrawing in which Fig. 1 is a longitudinal view, partly in section, ,of

invention; Fig. 2 is a detail view of part of the conductor employed inthe seal of Fig. l; and Fig. 3 is a view simliar to Fig. 1 of a modifiedform ofseal comprising my invention.

In carrying the invention into effect as illustrated, the seal consistsessentially of a thin strip of suitable metal I, such as molybdenum, toone end of which one or more strips of wire or ribbon 3, which may alsobe of molybdenum, are elec-. trically, welded. At the other end of stripl is secured one or more short pieces of metal foil 4 (Fig. 2) whichproject into a slot 5 formed in the end of a lead 6. When the pieces 4are inserted in the slot 5, they may be spot welded to make a goodelectrical connection.

The assembled conductor is inserted in a quartz or hard glass tube orsealing member 2 which has previously been compressed so as to form anenlargement I. The said tube is then closed at one end and, preferablythat end enclosing the lead 6, connected to a vacuum pump at the otherend. When the tube is evacuated and while still connected to the pump,the tube is fused down on to the molybdenum strip I, and to portions ofthe lead 6 and the strip 3 to form the stem or seal portion, as shown inFig. 1. The openend of the tube 2 is then sealed and disconnected fromthe vacuum pump, forming a chamber 9 in which the portion of the ribbon3 which projects be-- yond the seal is enclosed. This chamber forms atest chamber which can be used at any time to ascertain the condition ofthe seal. The'portion of electric of the tube surrounding the lead 8 maynow be removed by cutting it at the point l0 and the seal is thencomplete and can be stored until required. When the seal is to be putinto use, a spark test coil terminal can be applied to the exposed lead6. Should the seal be faulty, air will have leaked into the closedchamber and its presence will cause atypical glow when the test coil isenergized.

.In order to secure one of these seals into an envelope ll of refractoryvitreous material, an aperture 8 is blown in the wall of the envelope ofsufiicient diameter to enable the portion carrying the lead-in conductor6 to be inserted. The seal is then inserted into the aperture 8 untilthe edges of the aperture rest on the enlargedportion 1 of the seal. Theseal can then be joined to the envelop II by applying heat at the pointof contact of the envelope and the enlargement 'l and this heating willnot be sufilcient to cause any damage either to the ribbon 3 or theleadingin conductor 6. The evacuated chamber 9- protects the connectinglead 3 from oxidation and damage, and when the seal is secured to avessel and the device is complete, the chamber 9 maybe removed.

In the form shown in Fig. 1, the main portion of the seal is within theenvelope, but if desired it may be outside the envelope as shown in Fig.3, where the enlarged portion 1 is shown at the inner end of the seal.

As it is diificult to make a seal between quartz and a conductor, it isconvenient to make up seals as described above, so that they are instock when a particular piece of apparatus requiring them is urgentlyneeded.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. A seal for leading an electric conductor through the wall of avitreous envelope comprising a stem of refractory vitreous materialhaving a conducting member projecting from one end and a connecting leadextending from the other end and enclosed in an evacuated chamber formedintegral with the stem to prevent oxidation of and damage to said lead,said conducting member and connecting lead being electrically connectedwithin the stem and the stem being formed with an enlargement which canbe fused into an aperture in said envelope without the heat necessaryfor fusion deleteriously affecting said electric conductor. r

2. A seal for leading an electric conductor through the wall of avitreous envelope as claimed in claim 1 in which the conducting memberand the connecting lead are secured to oppositeends of a thin metalstrip hermetically sealed within the Stem.

' ERIC JOHN GEORGE BEESON.'

